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Wireless Power Transfer Using Simple Transistor Oscillator
In this experiment, I built a basic wireless power transfer system using components recovered from an SMPS power supply.
The transmitter circuit is based on a simple oscillator using an NPN transistor (C1301). I used a 10 Ω resistor and a 10490 capacitor connected in parallel to stabilize and assist the oscillation. The main coil was wound on a ferrite core with approximately 180 turns, and an additional feedback (primary) coil of about 30 turns was made using 28-gauge enameled copper wire.
When powered with a low voltage supply (around 1.5 V), the transistor starts oscillating, creating a rapidly changing magnetic field in the transmitter coil.
On the receiver side, I used a 5 mH inductor (salvaged from an LED bulb driver) connected directly to an LED. When this receiver coil is brought near the transmitter, the changing magnetic field induces a voltage in it, causing the LED to glow—demonstrating wireless energy transfer.
Before building the oscillator, I also observed a basic electromagnetic effect: when an air-core coil is connected and disconnected from a battery, the sudden change in current creates a changing magnetic field. This induces a voltage in a nearby coil, briefly lighting the LED. This happens due to electromagnetic induction, where collapsing magnetic fields generate high voltage spikes.